1. The Field of the Invention
This invention relates generally to optical packages containing optical devices, including, but not limited to, optical collimators, optical filters, optical circulators, optical isolators, and other optical devices. More particularly, the invention relates to sealing optical packages including optical devices.
2. The Relevant Technology
Optical networking and telecommunication is increasingly employed as a method by which information can be reliably transmitted via a communications network. Networks employing optical networking and telecommunication technology are known as optical communications networks, and are marked by high bandwidth and reliable, high-speed data transmission. During recent years, the discrete optical components or devices in such networks have become less expensive and are capable of being used with networks having increasing date transmission rates. In addition, optical networks are employed in a variety of conditions and environments, some of which tend to damage or interfere with the operation of the optical devices in the network.
Moisture penetration, for example, is one of the problems affecting optical device applications, particularly in an uncontrolled environment. Harmful moisture may penetrate through non-hermetically sealed devices by way of epoxy sealing areas. This harmful moisture can affect the performance of optical devices in many ways.
One way moisture can adversely affect the performance of optical devices is by increasing optical loss due to absorption of the optical light by moisture, in the form of water vapor, in the optical path. For optical devices working in wavelengths where moisture molecules have strong absorptions, the problem of increased optical loss is magnified.
In addition, moisture adversely affects optical device performance by increasing insertion loss by reducing the optical coupling. Increased insertion loss occurs in various ways. For example, moisture, in the form of liquid water, may condense on an optical surface of the optical device. This is likely to happen at low temperatures, for example during temperature cycling (−20° C. to 85° C.) rather than in the field. The presence of the moisture on the optical surface will deflect or scatter the initial light trajectory, and as a result, light cannot be effectively coupled into the receiving port. In addition, increased insertion loss occurs when an optical surface, such as a filter, is attached to another optical component, such as a collimator, by epoxy. In this case the moisture molecules can penetrate the epoxy seal, thereby creating volume expansion and eventually leading to optical misalignment.
In the manufacture of optical devices, components are most often sealed with epoxy. As discussed above, however, water molecules can enter the optical device through the epoxy seal, resulting in several problems, such as those illustrated above. The epoxy sealing can only slow, and not prevent, the moisture penetration.
Previous efforts to reduce penetration of moisture into the optical package have been to soldering or metallizing bonding interfaces. However, this process can be expensive because the bonding parts must be metallized and then soldered together. In some cases, the metallization coating, usually Au or Ni, may delaminate from the metal container surface and completely destroy the sealing.